As is well known in the art, tractor trailers use a coupling known as a fifth wheel where the trailer has one portion of the coupling and the truck or tractor unit has a further portion thereof. Conventionally, the fifth wheel construction for the truck unit comprises a substantially round flat plate to form a tractor bearing surface. The semi-trailer also includes a plate member with a king pin extending downwardly to locate and seat within a slot within the fifth wheel portion mounted on the truck unit. There are provided means for locking the king pin in place when the truck is put in position with the two portions of the fifth wheel engaging together.
Fifth wheel arrangements are used in a wide variety of applications to releasably couple the trailer to the tractor. The frames of the tractors to which the fifth wheel assemblies are mounted typically comprise a pair of longitudinally extending C-shaped frame members that are supported by the wheel on axle members of the vehicle. The frame members are laterally spaced apart from each other so as to provide a planer surface for resisting normal and twisting forces after the fifth wheel is secured thereto and placed in operation, thereby transferring the payload of the trailer onto the frame members.
The king pin receptor device generally may include a jaw assembly for securing the king pin of the trailer to the tractor. The jaws may be movable to secure and release the king pin extending from the trailer. There may also be an arrangement wherein the jaws are such that an operator can manually toggle the jaws between a position in which the king pin is secured to the jaws and a position in which the king pin is released from the jaws. When the king pin is secured in the jaws, the trailer is secured to the tractor and may be towed. When the king pin is released from the jaws, the king pin may be removed from the jaws decoupling the trailer from the tractor. An example of a king pin assembly is illustrated in U.S. Pat. No. 7,931,291 which is hereby incorporated by reference.
It is known in the art that friction between the two bearing surfaces develops and can lead to problems. In order to overcome this, it is known to place a lubricant between the two bearing surfaces. The lubricant, which is usually grease, helps but has not been found to be the solution since it is necessary to frequently replenish the grease. Moreover, the lubricant can be squeezed out of place and in cold weather, the lubricant can stiffen which can lead to handling performance problems and cause dangerous vehicle handling characteristics.